Which of the following filename extension suggests that the file is a backup copy of another file? A. BAK * B. BAS C. COM D. TXT E. None of the above

The correct answer is A. BAK.

A BAK file is a backup copy of another file. It is often used to create a copy of a file before making changes to it. This way, if the changes are not what you expected, you can always restore the original file.

The other options are not typically used for backup files. BAS files are batch files, COM files are executable files, and TXT files are text files.